Bert W. Rein, the attorney challenging Section 5, said that the South had changed and that the coverage formula should not have been reauthorized.

But Sotomayor cut him off. She said that even if some portions of the South had changed, "your county pretty much hasn't."

"Why would we vote in favor of a county whose record is the epitome of what caused the passage of this law to start with," she asked.

Justice Anthony Kennedy, who could be a crucial vote, asked a question that showed skepticism of Rein's position. He referred to Alabama's history of discrimination and noted that the state might be considered under any coverage formula.

"Why are you injured under this one?"

But as he had previously stated in a related case in 2009, Kennedy seemed concerned about the federalist implications of the law on the states. At one point he compared Alabama's sovereignty with the "trusteeship of the United States government."

Justice Elena Kagan defended the 15,000-page legislative record Congress developed after holding 21 hearings. "It's hard to see how Congress could have developed a better and more thorough legislative record than it did," she said.

Justice Clarence Thomas said nothing during arguments, but in 2009 he said he believed Section 5 " exceeded Congress' power to enforce the 15th Amendment."

In the audience were prominent civil rights activists, including the Rev. Jesse Jackson, the Rev. Al Sharpton, Rep. John Lewis, D-Ga., and Cecilia Marshall, the widow of former Supreme Court Justice Thurgood Marshall.

Protesters gathered on the steps outside the court before arguments began. They held signs with such messages as "Protect My Vote," and "My Vote, Our Rights, Our Fight."

Demonstrators from the Alliance for Justice lined up in front of the Supreme Court steps.

Jackson, Sharpton and Lewis spoke for the group, and were joined by Rep. Marcia Fudge, D-Ohio, House Minority Leader Nancy Pelosi, Rep. Judy Chu, D-Calif., and Ruben Hinojos, D-Texas, among others.

Fudge, chairwoman of the Congressional Black Caucus, had a clear retort to the arguments against Section 5: "You will not win. You will not win this battle."